High refractive index and good mechanical property UV-cured hybrid films containing zirconia nanoparticles

UV-curable zirconia (ZrO2) nanoparticle coatings, prepared by dispersing highly-crystalline zirconia nanoparticles (4 nm) in tetrahydrofuran with the aid of 3-glycidoxypropyltrimethoxysilane (GPTMS) and following addition of a cationic photoinitiator, were cast on silicon wafers (or glass substrates) by dip-coating or spin-coating and photopolymerized to get transparent ZrO2 nanoparticle films. Ellipsometrical characterization indicates that the refractive index of the film changes from 1.63 to 1.77 at wavelength of 632 nm when the molar ratio of GPTMS-to-ZrO2 decreases from 0.30 to 0.15. Nano-indentation tests show that the films exhibit robust mechanical performance though they are not heat-treated.